Cross-shot woven resistor



Sept. 1934- R. E. TARPLEY ET AL 1,972,720

CROSS SHOT WOVEN RESISTOR Filed Feb. 2. 1932 wvzmoas i eBa M ATTORNEYPatented Sept. 4, 1934 1,912,120 'cnoss-sno'r WOVEN nEsIs'roR Raymond E.Tarpley and Leo Behr, Philadelphia, Pa., assignors'to Leeds & NorthrupCompany, Philadelphia, Pa., a corporation of Pennsyl- Vania ApplicationFebruary 2, 1932, Serial No. 590,334

6 Claims. (Cl. 201-433) Our invention relates to resistors, orresistance units, having low or negligible inductance and capacity toensure thattheir time constant is low throughout a wide range offrequencies, and to permit their use in both direct current andalternating current measuring systems without intro duction ofappreciable errors.

In accordance with our invention, a resistor is woven on a suitablewarp, as of silk threads, from 10 two conductors lying side bysidethrough the tions of the warp elements are interchanged, as' I by theloom harness. At each end of the resistor,

the conductorsare connected together so that there is insubstantialdifference of potential between adjacent picks of conductor throughoutthe resistor, and because of the cross-shot weave the current flowsthrough adjacent picks in. opposite direction to eliminate inductiveeffects.

Our invention further resides in the methods of making resistors and inthe woven resistor hereinafter described and claimed.

For an understanding of our invention, reference is to be had to theaccompanying drawing in which: I

Fig. 1, on enlarged scale and with spacings exaggerated for'clarity,illustrates the weaving pattern of our resistor.

Fig. 2 is an explanatory figure.

Resistors for use with alternating current, or both direct andalternatingcurrents, in addition to the requirements of resistorssatisfactory for 40 direct. current measurements, should have thecharacteristic that their effective resistance is independent offrequency and their reactance negligible at least throughout asubstantial range of frequencies.

The ordinary resistor woven from a single resistance conductor does nothave this characteristic for it exhibits substantial inductance and itstime constant is therefore of substantial magnitude; further, forresistors of the same value of resistance and supposedly similar, thetime constants varied widely. It was and'is necessary with this type ofresistor to measure their individual time constant and then select thoseresistors-which are the least unsatisfactory for alternating currentuses, and even these selected resistors are not satisfactory, forexample they introduce large errors in phase angle measurements athigher frequencies, for example, 10,000 cycles and upwards.

In accordance with our invention, woven resistors can be made withtimeconstants so low that the error introduced for widely differentfrequencies is negligible, and for resistors of the same resistance andtype, the time constants are the same and do not vary widely as withsupposedly similar resistors as made heretofore.

Referring to Fig. 1 the pattern of weave results in a woven resistor ofvery low time constant, suited for high precision measurement. In thisresistor, the style of weave has been termed cross-shot, because it isformedby the simultaneous weaving of two conductors on the warp, thatis, one shuttle moves across the warp in one direction and anothershuttle moves across the warp in the opposite direction before theharness of the loom transposes the positions of the warp elements.

As clearly shown, the first pick p1 of conductor C, and the first pickP1 of conductor C1, lie side by side, that is, both pass under the samealternate warp'elements for example, 1, 3, 5, etc., and pass over everyother warp element as 2, 4, 6, etc. Specifically, both picks pass underthe warp element 101 at one selvedge edge and side by side passalternately over and under elements 102 to 107, both finally passingover warp element 1.08 at the other selvedge edge. Similarly, the

next pair of picks, p2 of conductor C, and pick P2 of conductor C1, lieside by side in the warp; Both pass over warp element wl, andalternately under and over elements 102 to w8, all as clearly indicatedin Fig. l, in which the size of the warp, of the conductors, and thespacing has been exaggerated to show clearly the relation of the picksto each other and to the warp elements.

In the completed resistor,the ends 1:, m1 of the different conductorswhich are of equal resistance are connected together, and the ends y,111 are likewise connected together. v

The effect of winding the resistor from two conductors as-described andconnecting them this manner is readily apparent from Fig. 2. In eachpair of picks p1, P1; p2, P2; p3, P3; etc., the current in one pick isflowing in one direction, while simultaneously current of thesame 105value is flowing in opposite direction through the otherpi'ck of thepair, so that in effect each pair of picks forms a short bifilarwinding.

From another aspect, it can be considered that the picks pl, 222, etc.,of conductor C form induchence practically negligible.

tive loops which are cumulative in their eiiect in causing the warpelements to be the cores of inductive solenoids, but the picks P1, P2,etc., of the conductor C1 also form inductive loops whose effects arecumulative but in opposition to the inductive effects of those ofconductor C, with the result that the inductive effects of theindividual windings annul each other; i. e. the individual warp elementsform the cores of noninductive solenoids. 1

Further as the adjacent picks of conductor throughout the warp are atsubstantially the same potential, the capacity effects are practicallynil. For example, the average effective residual of :1000 ohmcross-shot" woven resistors is about one micro-microfarad giving thevery low time constant of about .1 x 10" seconds. The resistance erroris about .001% for frequencies up to 50,000 cycles and even at muchhigher frequencies is within the limits of observation errors and Bycontrast, 1000 ohm resistors of simple weave have relatively largeinductive residuals which vary from about 4.5 to 12 micro'henries,introducing errors which are large for all resistors and which varygreatly for different resistors, of supposedly similar characteristics.

The resistance webbing may be mounted in any suitable manner, forexample, in any of the various ways shown in co-pending Tarpleyapplication Serial No. 586,518, filed January 14, 1932. The cross-shotwoven resistor is shown in the aforesaid Tarpley application but is nottherein claimed as it is our joint invention.

Another advantage of the cross-shot woveii resistor over the old type ofwoven resistor and over other types of low time constant woven resistorsdisclosed in the aforesaid application and using a single conductor isthat it facilitates weaving of resistors of the lower orders, i. e.,less than 1000 ohms for example. Since the conductors of our resistorare in parallel, electrically, the smaller sizes of wire, as #35 orsmaller, may be used, facilitating the weaving, and yet because of theparallel connection of the conductors comprising the resistor, its valueis low.

A resistor of the'same value of resistance, with a single wire ofsuitable fineness for weaving, is diflicult to calibrate accurately andfurther the total mass or area of wire is so small thatthe heat is notsufliciently dissipated by radiation to avoid the effect of temperatureupon the efiective value of the resistor. Both of these disadvantagesare overcome by our invention. v

Aside from the fact that the cross-shot weave is better suited for thelower values of resistance,

it has the further advantagethat the residual inductance for a givenresistance and given total cross-sectional area for the two wires isless than that of other woven resistors of the same resistance andcross-section shown in the aforesaid copending Tarpley application.

What we claim is:

1. The method of making a resistor having a low time constant whichcomprises simultaneously weaving two conductors on a warp in oppositedirections, and electrically connecting the ends of the conductors atthe same end of the warp to each other so that flow of current throughthe resistor willbe in opposite directions in adjoining similarlydisposed picks.

.2. The method of making aresistor having a lowtime constant, whichcomprises simultaneleading the conductors across the warp from oppositesides thereof, interchanging the positions. of the warp elements,leading both. conductors back through the warp in reverse directions,again interchanging the position of the warp elements, repeating theaforesaid sequence of operations to form a woven web, and connecting theends of the'conductor at the same end of the warp so that current inadjoining similarly disposed picks must flow in opposite directions. 7

3. The'method of making resistors to ensure low and similar timeconstants which comprises i forming each of said resistors bysimultaneously weaving two conductors on a warp, the adjacent picks ofthe difierent conductors lying side by side across the warp, andconnecting the ends of the conductors so that the current flows inopposite directions in the adjacent picks of the/conductors.

4. A resistor of low time constant comprising two continuous conductorscross-shotv woven back and forth on -a warp so that adjoining picks fromopposite sides of the warp lie side by side across the warp, and havingthe ends of the conductors at the same end of the warp connected 1115together electrically so that current in adjacent similarlydisppsedpicks mustiflow in OPDOsite directions.

' 5. A resistor of low time constant comprising two continuousconductors woven back and forth v through a warp and having theconductors connected together so that the currents in adjacentconductors lying side by side through the warp flow in oppositedirections.

3 RAYMOND E. TARPLEY.

LEO BEER. i

